Speedy Manhole Repair Completed Using EPP Grade Adjustment System

In early 2010, Narragansett Bay Commission (NBC) identified a manhole in Providence, R.I., as needing repair. The issue was that the manhole location on Putnam Pike (State Route 44) was directly in the wheel path of all traffic moving northwest on the highway. Due to the significant amount of traffic moving in both directions, a quick and easy but long-term repair was needed to minimize the impact on traffic during and after reconstruction. To complete the repair, the utility would be required to pay for a two-man police detail for traffic control in both directions, since only one lane would be accessible during the repair.

The Solution

A representative of Cretex Specialty Products had recently contacted NBC because the company was looking for field test sites to demonstrate a new product that was introduced earlier in the year. The new product was the Pro-Ring manhole and catch basin grade adjustment system, and it seemed like it could be a good fit for this repair. Pro-Ring is the first and only grade adjustment system made from expanded polypropylene (EPP), a high-strength, lightweight plastic that is suitable for replacing traditional construction methods using concrete grade rings, mortar or other masonry materials. This system was of interest to the city due to the many benefits claimed; it was said to be fast, safe and cost-effective, with one man being able to complete an entire adjustment in minutes. Since the system dramatically speeds repair time, it is more cost-effective. Using this system, a manhole repair site can be opened, reconstructed and closed in one day or less, reducing overall costs by as much as 20% to 30%. Since these grade rings weigh 95% less than concrete rings, they are much safer to use, minimizing the risk of worker injury.

On the day of the repair, crews and traffic control arrived and were set up by 7:30 a.m. The pavement was saw-cut, and the manhole was excavated and ready to be reconstructed by about 8:50 a.m. The installation of the Pro-Ring started at approximately 9:00 a.m. with some repair of the brick manhole using a high early strength repair mortar and then installing the adjustment rings and manhole frame casting. The installation was completed by 9:20 a.m., and the excavation was backfilled, compacted and prepared for the asphalt patch. Unfortunately, the asphalt did not arrive to the site until approximately noon, but once onsite, it was placed and compacted, with the entire repair being completed by 12:30 p.m. A short time later, the road was reopened to traffic in both directions, making the entire repair time from start to finish approximately five hours; if not for the delay in getting the asphalt to the site, it would have been repaired in less than four hours.

The completed installation prior to backfill and paving.

The Results

Since the installation almost seven years ago, the site has been subjected to an estimated 135,000,000 traffic impacts, and annual inspections show no negative effect on the Pro-Ring system or surrounding pavement repair.